The present invention relates to a novel solventborne coating material. The present invention further relates to the use of the novel solventborne coating material in automotive OEM finishing and refinish, in industrial coating, including coil coating, container coating and the coating of electrical components, in the coating of plastics, and in furniture coating. The present invention further relates to the use of the novel solventborne coating material for producing novel single-coat or multicoat clear or color and/or effect coating systems. The present invention relates not least to motor vehicle bodies, industrial components and finished products, including coils, containers and electrical components, polymer moldings, and furniture, which have at least one of these novel coating systems.
Coating materials referred to as conventional, i.e., coating materials containing solvent, continue to be indispensable for many end uses despite every attempt to replace them by solvent-free counterparts. For reasons of environmental protection and safety-related expenditure, however, manufacturers and users of solventborne coating materials are concerned to reduce further the solvent fraction of the coating materials, i.e., to achieve high solids contents. By those in the art, such coating materials with a high solids content are also referred to as “high-solids paints”.
The formulation of high-solids paints is particularly difficult for the technologically significant two-component paints which, as is known, are crosslinked using polyisocyanates. Thus high solids contents lead to an undesirably high coating material viscosity, which hinders spray application if not, indeed, preventing it entirely. Where, on the other hand, only constituents of low molecular mass, and thus of low viscosity, are used, the resulting coatings generally have an inadequate profile of properties. In general, the high solids content reduces the pot life of such coating materials to an unwanted extent.
It has proven possible to remedy the situation to a certain extent through the use of reactive diluents. A reactive diluent is a reactive diluting media or solvent which as defined in accordance with DIN 55945: 1996-09 becomes part of the binder by chemical reaction during film formation. When customary and known reactive diluents are used, for example, in coating materials, however, additional problems may occur, such as the partial dissolution of further coats on application or a lowering of the heat stability and the light stability. In addition, adding reactive diluents to the coating materials is an additional process step, which is fundamentally disadvantageous in the context of process economy.
There has been no lack of attempts to formulate high-solids paints which were to meet the continually growing technological requirements.
For instance, the European patent EP-A-0 638 591 discloses hydroxyl-containing copolymers having a particularly low viscosity which are obtainable by radical copolymerization of mixtures of olefinically unsaturated monomers that contain cycloaliphatic monomers. The hydroxyl groups in the copolymers are, sterically speaking, not very accessible, with the consequence that, although the two-component paints in question do have a longer processing capacity, this is obtained at the expense of a slowing of the crosslinking reaction.
The European patent EP-A-0 819 710 describes coating materials, especially two-component paints, based on graft copolymers and polyisocyanates. The graft copolymers in turn are based on functionalized polyolefins and monoepoxides, and are prepared preferably at high temperatures (150 to 220° C.). The coating materials, however, give coating systems whose gloss, acid resistance, scratch resistance, and leveling leave something to be desired.
The international patent application WO 97/30099 describes high-solids paints comprising aldimines and/or ketamines as reactive diluents and polyesters containing secondary hydroxyl groups as binders. These coating materials do give good coating systems, but the processing times and baking conditions must be observed very strictly.
Furthermore, the international patent application WO 96/20968 describes high-solids paints hydroxy-functional copolymers and oligoesters which are preparable by reacting at least one branched polycarboxylic acid with at least one monoepoxy ester and/or by reacting a polyol with a carboxylic anhydride and reacting the resultant intermediate with an epoxide. The coating systems produced with these known coating materials also require further improvement in respect of their gloss, acid resistance, scratch resistance, and leveling.